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Friday, September 01, 2017

Arnie Coro's Dxers Unlimited

Mid-week edition: 29 August 2017

Hi amigos radioaficionados all around the world now enjoying the slightly better short wave propagation conditions that happen as we approach the autumn equinox !!! Propagation conditions on the HF bands from 20 to 6 meters have taken a turn for the better, especially within the frequency range between 14 and 25 megaHertz!

I am your host Arnie Coro, radio amateur CO2KK, also having a good time listening to the the HF bands although the solar flux is hovering just near 80 units. Near Vertical Incidence Skywave propagation mode continues to provide short range communications during the daytime, especially on the 40 meters amateur band.

Item two: Some of the world's prominent solar scientists are really concerned about the possibility of an upcoming second edition of the so called Maunder Minimum, when the Sun stopped from generating sunspots for a period of around 70 years... Other scientists believe that the abnormal behavior of the present solar cycle is not as bad as initially thought, something that we are all hoping to be what would happen... If solar cycle 25, the next one, shows a very slow start up period, then radio amateurs around the world will have to deal with a situation at least as worse as the final years of cycle 23, when extended periods without sunspots left the higher bands dead for weeks and months...

Item three: Here at the mid week edition of Dxers Unlimited, coming to you from Havana amigos... No HF propagation, no sunspots, or very weak solar activity does not mean that the amateur radio hobby will go down the drain... Hopefully there are several very interesting options that range from the extended use of the very low and low frequency bands by means of advanced digital communications protocols to the launching of many more ham radio satellites, including perhaps , if funding can be found, the placing in orbit of several Molnya type satellites... or we can even dream of one or two geostationary ham radio satellites !!!

The present day amateur radio satellites are all orbiting the Earth at rather low altitudes, so their coverage is limited to a rather small footprint. In other words, the small footprint means that the time slot available to communicate between two stations operating via satellite is only a few minutes, even during the best passes... The fact that today's satellites are at such low height is what in my opinion have prevented more radio amateurs from experimenting with this type of space link...

As a young ham said to me during a satellite communications conference that took place at the venue of the Cuban Federation of Radio Amateurs here in Havana, it is barely worthwhile to build special antennas , install tracking software and learn how to use it, plus having to obtain VHF and UHF equipment capable of operating on Single Side Band and CW modes, only to enjoy perhapes two or three daily brief periods when the satellites that are operational can be reached from the place where one is located.

In a certain way the young ham is right... my perception is that a single new satellite placed at a much higher Earth orbit, so that the time window available for its use could reach at least half an hour four times every day will dramatically change the number of ham radio satellite users, to the present very few to a much larger number of experimenters...

Although the availability of dual band 2 meters and 70 centimeters FM handie talkies that can access the FM repeater type of satellites using a small dual YAGI hand held antenna , has increased the number of users of those satellites, at this moment what everyone is waiting for is for a satellite that could ride piggyback on one of the many professional geostationary birds that are constantly been launched. But so far, the owners of those expensive satellites, that are worth hundreds of millions of dollars have not accepted the risks involved in providing extra space and electric power to a ham radio satellite that will form part of such a package. Insurance companies will not accept an extra satellite without the proper certification of compliance with many complex technical regulations….
In the meantime, there is still another very interesting Earth orbiting spaceship... the International Space Station that is fully equipped to operate on several amateur bands... The ISS is active from its low Earth orbit, and whenever the crew members that are licensed amateur operators decide to take a break, they communicate with fellow hams all around the world !!!

You have questions and your amigo Arnie tries to answer them as soon as possible, directly to your e-mail or postal address and also on the air too... Today's question came from five different locations, Argentina, Guyana, South Africa, the USA and New Zealand....

Dxers Unlimited's listeners in those five countries want to know more about the SLIM JIM low take off angle vertically polarized antenna , especially the one designed to work on the world's most popular ham band.. 2 meters. There is a worldwide agreement that specifies the use of narrowband FM on the two meters band , using vertical polarization... At this moment there are more amateur radio stations in the world using the two meters band on the FM mode with vertically polarized antennas than in any other ham band... So, 2 meters band vertically polarized antennas are very popular, and because they are easy to homebrew and can be made with low cost materials, it is a fact that those antennas are really popular projects.

Among 2 meters band vertical antennas that are easy to make and show good performance, my favorite is the SLIM JIM, a type of folded monopole that when properly build and installed is capable of producing a very nice low take off angle vertical antenna pattern, exactly what you need to communicate via ground wave.

As a matter of fact the SLIM JIM two meters band vertical shows a much better performance than a half wave dipole at the same height, and that is way the British designed SLIM JIM has become so popular among the millions of hams around the world that communicate with each other using the 2 meters band...

And now that I am talking about what according to my own personal experience is the most efficient single element omnidirectional vertically polarized antenna for the two meters band, the SLIM JIM, let me add that the easiest to build and tremendously effective directional antenna for two meters also originated in the United Kingdom... It was created by Les Moxon, and for that reason is known as just as the MOXON, or better yet as the MOXON Rectangle antenna... that has a very high front to back ratio, plus an extremely wide horizontal pattern coverage...

In an upcoming edition of Dxers Unlimited, and at the request of several listeners , I will provide you with more information about the MOXON rectangle antenna that is now also becoming very popular among ham radio operators that are using them on the 20, 17, 15 , 12 , 10 and 6 meter bands... But let me add that they are single band antennas.... although I as have just said, the MOXON is a single band directional antenna system...

And now amigos, just at the end of our mid week edition, here is Arnie Coro's HF plus low VHF band propagation update and forecast...

Expect soon to starttheTRANS EQUATORIAL PROPAGATION season that this year may be an early starter. Solar flux hovering between 75 and 80 units and the night time maximum usable frequency nose diving even below 7 megaHertz...Don't forget to send your signal reports and comments about this and other RHC programs to inforhc@enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba